The present invention relates to a process for producing foam cushions, and, in particular, polyurethane foam cushions, with sections of different hardnesses. In the process, at least two liquid reaction mixtures, which form foams of different hardnesses are fed one after another into a mold cavity. The second reaction mixture is already creamed up when it is fed into the mold. The foam cushion is then removed from the mold once the reactions are complete.
The production of foam cushions having sections of different hardnesses using foam molding techniques is known (see, e.g., U.S. Pat. Nos. 4,190,697 and 4,379,856, and European Patent Nos. 0,068,820 and 0,056,939). Common to these processes is the fact that the exact position and extension of the sections of different hardnesses is difficult to reproduce. Such processes therefore present problems in mass production, particularly in the automotive industry. Thus, the desired properties, such as side guide forces of cushioned seats for the passengers, cannot be obtained.
It is also known (see, e.g., German Offenlegungsschrift No. 2,052,907) that when producing cushions with sections of different hardness, a fabric should be inserted in the cavity of the mold. These fabric inserts are typically arranged vertically or slightly tilted. The different reaction mixtures are fed in simultaneously and on both sides of this insert. The reaction mixtures and the foams that are formed can penetrate into both sides of the insert. A perforation which allows the penetration of a highly liquid reaction mixture is not intended for these porous sheets.
The object of the present invention was to improve the above-mentioned processes with respect to the ability to reproduce the exact position and extension of the individual sections in the cushion produced.